306 LEAD IN VARIOUS ARTIFICIAL PRODUCTS. 
the error to which crystal glass might lead in legal cases, 
in treating, as was then usual, matters suspected to contain 
arsenic with carbonaceous matters in glass tubes containing 
oxide of lead. ( Vide my letter addressed to M. Lefra^ais- 
Lalande, printed in a memoir of M. Guerre, Advocate at Ly- 
ons, for the defence of Mde. D. indicted for parricide.) The 
same fact, I mean the existence of oxide of lead in glass, 
might lead to an erroneous result, not only in medico-legal 
investigations, but in any research whatever. Hence, to 
obviate any possible error, I call to mind the discussion 
raised by several chemists, with reference to the presence 
of oxide of lead in reagents, and especially in potassa pre- 
pared by alcohol. 
According to M. Dupasquier, of Lyons, known to the 
Academy by his interesting labors in several branches of 
chemistry, the potassa prepared with Alcohol, as sold by the 
manufacturers of chemical products at Paris, contains oxide 
of lead. According to M. Louyet, of Brussels, who inves- 
tigated the absorption of deleterious substances by plants, 
the potassa prepared by alcohol by the firm of Robiquet, 
Boyveau,and Pelletier, is entirely free from them, contain- 
ing, however, small quantities of alum, silica, and platinum. 
Without pretending to obtrude myself as an arbitrator 
between MM. Dupasquier and Louyet, it evidently results 
from my own observations that alkalis, potassa, soda, ba- 
ryta, strontia, and lime, though deprived of oxide of lead, 
on being kept dissolved in flasks of glass, containing lead, 
may dissolve a notable quantity of this oxide. 
Finally, on terminating this note, I consider it useful to 
quote the following passage, extracted from a report laid 
before the Academy : — 
" The frequent use made in our days of several poisonous 
compounds, as those of arsenic, copper, &c. &c, must ex- 
cite our attention,Tor it is possible, for instance, that waters 
which have served to wash substances impregnated with 
arsenical compounds, might in some places have a pernicious 
